using System.Text.Json;

namespace Nonemm.Recorder;

/// Reads and writes the one configuration file.
public sealed class RecorderConfigStore
{
    private static readonly JsonSerializerOptions Options = new() { WriteIndented = true };

    private readonly string path;

    public RecorderConfigStore(string path)
    {
        this.path = path;
    }

    public static string DefaultPath()
    {
        string folder = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
        return Path.Combine(folder, "nonemm-recorder", "config.json");
    }

    /// A missing file gives the default configuration. A file that cannot be
    /// read throws, so a damaged file is not replaced without the operator
    /// knowing.
    public RecorderConfig Load()
    {
        if (!File.Exists(path))
        {
            return new RecorderConfig();
        }
        try
        {
            using FileStream stream = File.OpenRead(path);
            return JsonSerializer.Deserialize<RecorderConfig>(stream, Options) ?? new RecorderConfig();
        }
        catch (JsonException cause)
        {
            throw new InvalidDataException($"{path} is not a recorder configuration", cause);
        }
    }

    public void Save(RecorderConfig config)
    {
        Directory.CreateDirectory(Path.GetDirectoryName(path)!);
        string temporary = path + ".tmp";
        File.WriteAllText(temporary, JsonSerializer.Serialize(config, Options));
        File.Move(temporary, path, overwrite: true);
    }
}